There is a technology in which a commodity is recognized from an image captured by an image capturing section. As one example of the technology, there is a technology in which a code symbol such as a barcode and the like attached to a commodity is read from an image obtained by photographing the commodity, and then the commodity is recognized. As another example, there is also a technology in which an appearance feature amount of a commodity is extracted from an image obtained by photographing the commodity, and the commodity is recognized based on the feature amount data.
As all of these commodity recognition apparatuses need to achieve the brightness required to capture an image, a commodity serving as an image capturing object is irradiated with an illumination light. However, if the luminance of the image is too high, the commodity recognition apparatus cannot recognize the commodity. Therefore, the commodity recognition apparatus calculates the luminance of the captured image, and temporarily reduces the light quantity of the illumination light every time the luminance of the captured image exceeds a given luminance. In this way, the commodity recognition apparatus dynamically adjusts the luminance for each image to improve the recognition rate.